Food container (or lunch box) is one of essential goods during having meals. A conventional lunch box generally includes a container to hold the foods that is sealed by a lid to keep the foods clean. Most of the conventional lunch boxes are made of metal (such as stainless steel). However, nowadays most people are busy in work, especially students or office workers, few have time to prepare lunch or care much about preparing lunch. Hence eating out becomes a rising choice for many people. Most of the food containers used for eating out are microwave-enabled, such as those sold in convenience stores and mainly made of PP (polypropylene), with a transparent lid to enable consumers to see the food inside to decide whether to buy or not.
U.S. Pat. No. 6,883,678 entitled “Food container sealing structure” includes a body and a cover. The body and cover have respectively a flange on the rim that has a transverse edge and a longitudinal edge. The transverse edge of the cover has a first annular rib coupled to a first annular groove formed on the transverse edge of the body. The longitudinal edge of the cover has a second annular rib latched with a second annular groove formed on the longitudinal edge of the body. Through the first and second annular grooves and first and second annular ribs, the cover and body can be latched tightly to seal foods in the container.
However, the aforesaid conventional technique still has drawbacks, notably the first annular groove and first annular rib formed respectively on the transverse edges of the body and cover diminish the transverse support strength. Hence the cover is easily deformed and displaced when being subject to forces from users, and results in unsecured latching between the second annular rib and second annular groove on the longitudinal edges of the body and cover. Moreover, due to dimensional errors always taking place during injection molding of plastic products, the dimensional errors among the first annular rib and groove and the second annular rib and groove make the cover could not be fully covered on the body, and result in easy separation or non-tightness. Liquid foodstuff held in the body could be leaked out as well.